Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The only behavioral hint the description adds is 'for voice,' which weakly implies an output format, while the rest of the sentence enumerates unrelated app content. It omits return shape, line pagination, and how defaults (today, first card) resolve.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description duplicates the title verbatim (including a doubled period), then spends its longest sentence on catalog copy that does not describe this tool. It is not wasteful in length, but it is poorly front-loaded and the second sentence does not earn its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With zero required parameters, an optional n/date/reading trio, and no output schema, the definition should clarify the reading/card granularity and its relationship to get_reading and get_today, which remain ambiguous. Instead it substitutes app-marketing text for the information an agent needs to invoke it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% (n, date, and reading are each documented with defaults), so the schema already carries parameter meaning. The description adds nothing about card numbering, date handling, or reading-id sourcing beyond the schema. Baseline 3 applies when the schema does the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The opening sentence largely restates the title ('Today's reading one line at a time, for voice') rather than stating a distinct verb+resource, and the second sentence catalogs the whole app's content (plans, search, Meditations, Enchiridion, letters) instead of describing what get_card returns. An agent cannot tell from this text how get_card differs from siblings like get_reading or get_today. Only the fragment 'one line at a time' hints at the granularity.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no when-to-use, when-not-to-use, or alternative-selection guidance. The words 'plans' and 'search' appear only as content enumeration, not as routing cues, and could even mislead an agent toward search_readings or list_readings. The agent gets no signal for choosing get_card over get_reading.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.